Electrostatic recording device utilizing the electric potential in a discharge space

ABSTRACT

The device comprises known means for making a gas discharge scan a plurality of scan electrodes. A plurality of voltage inducing electrodes are placed in the space which the discharge traverses. The electric potential assumes a certain definite distribution in the space between the firing one of the scan electrodes and the opposing electrode due to the electric conductivity produced in the space by the discharge. Means is provided for varying the space voltage in compliance with an electric signal. The voltage inducing electrodes are led out of the space to a row of styli, respectively. The voltage supplied successively to the styli is used to produce a record of the signal on an electrostatic recording medium which represents a high impedance against the induced voltage and which is fed transverse to the row of the styli.

United States Patent 11 1 Ohkubo et al.

1 1 July 31, 1973 ELECTROSTATIC RECORDING DEVICE FOREIGN PATENTS 0R APPLICATIONS UTILIZING TIIE ELECTRIC POTENTIAL IN 638 916 3,1962 Canada 346/74 ES A DISCHARGE SPACE [75] Invemms: Tosh?) Ohkubo; Kazuoiyafli a Primary ExaminerStanley M. Urynowicz, Jr.

Yoshlzum' Terazawaean Tokyo, Attorney-Richard C. Sughrue et al. Japan [7 3] Assignee: Nippon Electric Company, Limit ed," 57 ABSTRACT Tokyojapan The device comprises known means for making a gas [22] Fil d; N 16, 1971 discharge scan a plurality of scan electrodes. A plurality of voltage inducing electrodes are placed in the PP 199,225 space'which the discharge traverses. The electric potential assumes a certain definite distribution in the [30] Foreign Application Priority Data space between the firing one of the scan electrodes and Nov. 20 1970 Japan 45/102881 the PP s eleetrede due to the electric Conductivity Dec 21 1970 Japan 45/116285 Pmduced the 8Pace by the discharge Means is P vided for varying the space voltage in compliance with 521 US. (:1. 346/74 ES, 313/196 an electric signal- The vehege inducing electrodes are 511 1111. c1. G01d 15/06 led out of the Space to e few O Styli, reepeetively- The 581 Field of Search 346/74 ES, 74 EB, voltage pp successively t9 the Styli is used to p 346/74 313/192 196, 197, duce a record of the signal on an electrostatic record- 179/1002 MD ing medium which represents a high impedance against the induced voltage and which is fed transverse to the [56] References Cited row of the Sty!" UNITED STATES PATENTS 21 Claims, 8 Drawing Figures 3,209,324 9/1965 Diamond et al 179/1001 MD II A 1 K= 30 l4-l 14-2 l4-3 1e- 2 4 e e IZ-O l2-6 l2-7 W31 .4 1 hrmr K 23 lZ-l l2-2 l2-3 22 .JIL

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saw u or 4 H1? HQBH 4| 42 43 SWITCH SWITCH START GUIDE PULSE GEN PULSE GEN ELECTROSTATIC RECORDING DEVICE UTILIZING THE ELECTRIC POTENTIAL IN A DISCHARGE SPACE BACKGROUND OF THE INVENTION This invention relates to an electrostatic recording device which is frequently used in an electronic printing device, a facsimile receiver, and the like.

. Conventional electrostatic recording devices can broadly be classified into a mechanical scanning type and a cathode-ray tube type. The former comprises a large number of styli arranged electrically insulated from one another in such a manner that their ends on the one side are aligned along a straight line, with the end surfaces adapted to be brought into contact with an electrostatic recording paper, and that the other end portions are arranged along a cylindrical surface and cyclically supplied with the picture signal by means of a brush rotated by an electric motor to scan the styli at the side or the end surface of the cylinder. Due to the mechanical scanning, the device of this type is disadvantageous in that the scanning speed is about 1,000 lines per minute at most and that the maintenance is troublesome because of the wear and the possible damage caused by the contact between the rotating brush and the styli.

The latter comprises a cathode-ray tube of a sort having a large number of stylus-like conductors planted through the face plate along a horizontal line of scan instead of the usual fluroescent material. The electron beam intensity-modulated by the picture signal is caused to scan the conductors to give negative electric charges to the conductors by the secondary electron emission. The negative charges are used to form an electrostatic latent image on an electrostatic recording medium fed perpendicular to the row of the conductors. By virtue of the electronic scanning, it is possible with the devices of this type to attain a high scanning speed and to get rid of the mechanical wear and damages. The devices, however, are objectionable in that the electron tube is of a specific construction, accordingly expensive, and in need of a high operating voltage of to 30 kilovolts and that the peripheral circuits require troublesome adjustment of the beam position, deflection, and'linearity, complicated circuitry for correction of the distortion in the beam deflection, and a high withstand voltage due to the fact that the tube is put into operation with the anode grounded.

SUMMARY OF THE lNVENTlON lt is'therefore anobject-of the present invention to provide an electrostatic-recording device of a third type which is different from the mechanical scanning type and the cathode-ray-tube type.

It is another object to provide an electrostatic recording device which is inexpensive and easy to adjust and to maintain as compared with the devices of the mechanical scanning and the cathode-ray tube types.

It is still another object to provide an electrostatic recording device that affords a higher scanning speed than the devices of the mechanical scanning type.

ltis yet another object to provide an electrostatic recording device that works with lower voltage than the devices of the cathode-ray tube type. The voltage required for the devices according to this invention is less than one kilovolt.

A further object of the instant invention is to provide an electrostatic recording device which requires a lower signal voltage but is substantially entirely free from the possible failure of the scanning.

It is already known that when a gas discharge is started between one of a plurality of aligned cathodes and a common anode, the ions produced thereby couple. the adjacent cathodes to lower the firing potential at such cathodes and that the discharge scans the cathodes when the aligned cathodes are successively supplied with a pulse which is about volts negative with respect to the electric potential at the remaining cathodes. The application, however, has been limited to discharge counter tubes wherein use is made of the electric signals produced in the external circuit connected to the cathodes and to indicator tubes wherein the glow of the discharge is directly observed by eyes.

According to the present invention, it is noticed that the space near the discharge has a high electric conductivity and travels along the row of the cathodes as the discharge scans the cathodes and that it is possible to induce the electric potential of the discharge space in an electrode placed in the discharge space. In view of the fact that the anode and the cathode are interchangeable under the circumstances considered, the cathodes scanned by the discharge and the anode are herein calledwthe scan electrodes" and the "opposing electrode", respectively. The electrode in which the space electric potential is induced is called herein the voltage inducing electrode". Furthermore, it is found possible to modulate the space electric potential in compliance with an electric signal.

lt has been confirmed that the induced voltage is equivalent to the voltage supplied by a power source having a very high internal impedance. lt should therefore be understood that the induced voltage has not a wide field of application. The induced voltage, however, can provide considerable electric power when supplied across a sufficiently high-impedance load. such as an electrostatic recording paper. The voltage inducingelectrode disposed near the anode delivers somewhat higher induced voltage than that situated near the cathode and shows several times as large an internal impedance as that shown by the latter because the ion density near the anode is smaller than that near the cathode.

The induced voltageis approximately equal to the socalled normalcathode drop. The cathode drop'assumes various values depending on the combination of the material of the cathode and the gas in which the discharge takes place. The highest value may be 475 volts for the cathode of platinum and the gas of carbon dioxide. On the other hand, it is already known that when the electrostatic latent image produced on an electrostatic recording medium is developed by way of the brush method, no recognizable record is obtained for the voltage less than about 300 volts while the maximum degree of black is produced for the voltage of about 800 volts. 'lt is'therefore desirable that the induced voltage applied across the recording mediumbe varied by the picture signal between 300 volts and'S'OO volts. When the development is accomplished with a toner of positive polarity, it is possible to use a negative picture signal voltage to derive a negative output voltage.

Means for modulating the induced voltage by an electric signal may be means for simultaneously supplying the signal across the scan electrode and the back electrode for the electrostatic recording medium. The voltage inducing electrodes successively derive the output voltage which is equal to the sum of the voltage difference between the firing one of the scan electrodes and the voltage inducing electrode subjected to the gas discharge plus the signal voltage superimposed thereon. Alternatively, the means may be means for varying the discharge current in compliance with the signal in view of the fact that the induced voltage becomes higher with increase in the discharge current. The former requires somewhat higher signal voltage than the latter. With the former. it is furthermore necessary either to lower the output impedance of the picture signal source or to isolate the picture signal voltage from the negative pulse voltage for causing the discharge to scan the scan electrodes when the frequency of the picture signal is very high. With the latter, scanning may become unstable when the ion coupling indispensable to the scanning becomes insufficient as a result of too reduced discharge current. Although it has been confirmed that an electrostatic recording device mentioned above works satisfactorily in any event, another means for modulating the induced voltage is offered in the following.

It is known that when two voltage regulator tubes are connected in series with the same forward direction and supplied with a dc. voltage through a ballast resistor, the voltage across the cathode and the anode at the both ends is approximately twice as high as that produced across a single voltage regulator tube. In addition, it is usual in a facsimile system to record the picture signal on two levels of white and black. This makes it possible to represent the picture signal with the binary logical values of and I.

In accordance with an aspect of the instant invention, two kinds of discharge paths are provided, the discharge path of one kind through two voltage regulator tubes connected in series with the same forward direction and the discharge path of the other kind through one of the two regulator tubes. The voltage inducing electrodes are placed in the respective discharge paths of the above-mentioned one kind at the voltage regulator tubes that are different from those providing the discharge paths of the other kind. Means is provided for activating the discharge paths of the abovementioned one kind when the picture signal assumes the value of logical l and for activating the discharge paths of the other kind when the picture signal assumes the value of logical 0.

The pitch of the scan electrodes is preferably not less than 0.4 millimeter while the pitch of the styli is preferably not greater than 0.25 millimeter to provide the desirable resolution. In order to reduce the dimensions of the device, it is possible to align the scan or-the voltage inducing electrodes along a circle, an ellipse, or the like. The opposing electrode may be divided into a plurality of electrode portions; in other words, the gas discharge tube may have a plurality of anodes to provide restricted discharge regions and to reduce the unwanted mutual interference between the voltages successively induced in the adjacent voltage inducing electrodes. lnterswitching of the discharge paths is not adversely affected by the deionization time, which is less than about 500 microseconds for inert gases and less than about microseconds for hydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram for explaining the principles of the present invention;

FIG. 2 is a graphical representation of the results obtained by the circuit shown in FIG. '1;

FIG. 3 schematically shows a first embodiment of this invention;

FIG. 4 schematically shows a second embodiment of the invention;

FIG. 5 schematically shows a third embodiment of the invention;

FIG. 6 is an exploded perspective view of a practical arrangement for a gas discharge tube to be used in the second and the third embodiments of this invention;

FIG. 7 schematically shows a fourth embodiment of the instant invention; and

FIG. 8 schematically shows a fragmentary perspective view of a practical arrangement of a gas discharge tube to be used in the fourth embodiment, with a part cut away.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a test discharge tube 1 1 for measuring the characteristics of the voltage inducing phenomenon in accordance with the present invention comprises a cathode 12, an anode 13, and a voltage in ducing electrode 14 disposed near the cathode 12. The anode 13 is connected through an ammeter 15 for measuring the anode current and a ballast resistor 16 to the positive terminal of a do power source 17 for causing a glow discharge to take place between the anode 13 and the cathode 12. The voltage inducingclcctrode 14 is connected to a load resistor 18 having a shunting voltmeter 19 of a sufficiently high internal resistance for measuring the induced voltage.

In FIG. 2, a curve in full line indicatesthe results measured with the circuit shown in FIG. 1, wherein the cathode 12 is of nickel and the gas sealed in is neon at 60 mmHg and the anode current is kept at a constant value of 1.4 milliamperes with the load resistance of the resistor 18 varied from 50 kilohms to 10 megohms. Another curve in dashed line represents the following equation:

where E is the induced voltage in volts and R is the load resistance in megohms. Inasmuch as these two curves are in excellent coincidence, the induced voltage is considered to be equivalent to the voltage supplied by a source having an open-circuit voltage of volts and an internal resistance of 1.3 megohms.

Referring to FIG. 3, a first embodiment of the instant invention includes a gas discharge tube 11A comprising a line start cathode 12-0, a set of discharge path cathodes 12-1, 12-2, 12-3, arranged in alignment to the right (in the drawing) of the start cathode 12-0 and intervened by a set of aligned discharge guide cathodes 12-6, 12-7, 12-8, each cathode being provided with a hollow metal cylinder and a fine-pointed metal projection 12' projecting therefrom for determining the sense of scan of discharge. The start cathode 12-0 need not be provided with the projection. The tube 11A further comprises a common anode 13and a plurality of voltage inducing electrodes 14-1,14-2, 14-3, opposing the cathodes 12-0, 12-1, -12-6, and in the vicinity of the discharge path cathodes 12-1, 12-2, 12-3, respectively. Between the discharge path cathodes 12-1, 12-2, 12-3, and the anode 13, a d.c. power source 17 supplies the discharge voltage through a ballast resistor 16. The start cathode 12-0 is led out of the tube 11A to a line start pulse terminal 20 through a first pulse transformer 21. The guide cathodes 12-6, 12-7, 12-8, are led out to a common guide pulse terminal 22 through a second pulse transformer 23. The voltage inducing electrodes 14-1, 14-2, 14-3, are led out to a plurality of styli 24-1, 24-2, 24-3, respectively, for applying the induced voltage across an electrostatic recording paper 25 placed on a back electrode 26. The embodiment further comprises a picture signal terminal 28 connected to the discharge path cathodes 12-1, 12-2, 12-3, through a bias source 29.

in operation, the discharge takes place between the start cathode 12-0 and the anode 13 when a line start pulse voltage negative with respect to the reference potential at the picture signal terminal 28 is applied to the start pulse terminal 20. As the guide pulse terminal 22 is supplied with a guide pulse voltage 32 negative with respect to the reference potential, the discharge moves from the start cathode 12-0 to the first guide cathode 12-6, therefrom to the second guide cathode 12-7, and so on. The arrangement and operation in this connection is already known as regards single-pulse discharge counter tubes having concave cathodes, described in HATTA-Yosinori, Tohoku Daigaku Kiso Densi-kogaku Nyumon Koza (Tohoku University Fundamental Electronics Guide Books"), Vol. 9, Hodenkan" (Discharge Tube"), pp. 95-96, published by Kindai-Kagaku-Sya,- Nov. 10, 1962. The bias source 29 serves to make each of the discharge path cathodes 12-1, 12-2, 12-3, participate in discharge while being traversed by the discharge. When the discharge reaches the first discharge path cathode 12-1, the associated voltage inducing electrode 14-1 supplies the stylus 24-1 with an electric potential equal to the instantaneous voltage of the picture signal supplied across the picture signal terminal 28 and ground plus the voltage difference between the discharge path cathode 12-1 and the voltage inducing electrode 14-1 minus the voltage of the bias source 29. in this manner, the following styli 24-2, 24-3, are successively supplied with electric potential which is determined by the instantaneous voltage of the picture signal. A line synchronizing signal contained in the picture signal makes the line start pulse voltage 30 assume a second negative-going pulse voltage in the manner conventional in the art to restart the scanning. Meanwhile, the recording paper 25 is continuously fed perpendicular to the plane of FIG. 3. With the arrangement designed to make the electric potential at the styli 24-1, 24-2, 24-3, successively vary between about 300 volts and 800 volts as the picture signal voltage varies between the white level and the black, it is understood that the picture signal provides an electrostatic latent image on the recording paper 25.

The pulse transformers 21 and 23 make it possible to ground the pulse generators (not shown) for the start and the guide pulse voltages 30 and 32 and to isolate the picture signal from the pulse voltages 30 and 32 and may be dispensed with when the frequency of the picture signal is not very high. Alternatively, the picture signal may be applied between the back electrode 26 and ground, with the terminal 28 of the reference. po-

tential or the negative terminal of the d.c. power source 17 grounded. I

For the embodiment illustrated with reference to FIG. 3, it is possible to employ the scanning mechanism of a single-pulse discharge counter tube, either having a peripheral circuit comprising a parallel circuit of a resistor and a capacitor or having a plurality of discharge guide cathodes for each discharge path cathode. it is, however, to be noted that those having many guide cathodes are inconvenient because of the somewhat complicated structure and the larger dimensions of the whole apparatus.

Referring to FIG. 4, a second embodiment of the present invention is similar to the first embodiment as regards the elements depicted with the same reference numerals and operates in compliance with the scanning mechanism of a double-pulse discharge counter tube. The discharge tube 118 of the second embodiment comprises a first set of cathodes 12-1 1, 12-12, a second set of cathodes 12-21, 12-22, and a third set of cathodes 12-31, 12-32, led out of the tube 118 to a first, a second, and a third guide pulse terminal 41, 42, and 43, respectively, and aligned along a line together with the line start cathode l2-0 with the order of the cathodes 12-0, 12-11, 12-21, 12-31, 12-12, 12-22, 12-32, The voltage inducing electrodes 14-1, 14-2, 14-3, are disposed adjacent the respective cathodes 12-11, 12-21, 12-31, Another voltage inducing elec- I trode 14-0 may be placed adjacent the start cathode 12-0. The terminal 28 of the reference potential is connected to the negative terminal of the d.c. power source 17. Guide pulses going negative with respect to the reference potential and having a delay substantially equal to the common pulse width are cyclically supplied to the guide pulse terminals 41, 42, and 43 from a three-phase guide pulse generator (not shown) producing three-phase guide pulse voltages 46, 47, and 48, each having a duty ratio substantially equal to 1:3. This makes the discharge started at the start cathode 12-0 scan the remaining cathodes in the sense determined by the phase relation of the guide pulses. With the scanning mechanism of a double-pulse discharge counter tube, it is unnecessary to provide the projections 12' and the bias source 29 described in connection with the first embodiment. Pulse transformers (not shown) may be provided either to isolate the picture signal from the pulse voltages 30, 46, 47, and 48 or to make it further possible to ground the start and the guide pulse generators. The picture signal may be applied between the back electrode 26 and ground.

Referring to FIG. 5, a third embodiment of the present invention is quite similar to the second embodiment and comprises the elements illustrated with the same reference numerals. except a discharge current control circuit 50 used instead of the ballast resistor 16 and a bias source connected in series to the d.c. power source 17 between the negative terminal of the latter and ground. For the third embodiment, the potential at the junction 28 between the negative terminal of the d.c. power source 17 and the positive terminal of the bias source 55 is used as the reference potential. The picture signal is supplied across a pair of picture signal terminals 58 and 59 of the control circuit 50 to control the discharge current, thereby varying the potential induced in that one of the voltage inducing electrodes 14-0, 14-1, 14-2, 14-3, which the discharge traverses. The bias source 55 serves to supply the successive ones of the styli 24-0, 24-1, 24-2, 24-3, with the electric potential desirable for the electrostatic recording medium 25.

With a discharge tube 118 used in the second or the third embodiment, it has been found possible to use such guide pulse voltages 46, 47, and 48 as may have as short a pulse width as 23 microseconds and thus to scan the width of an electrostatic recording paper 25 of the A4 size about 3,000 times per minute with resolution of four points per millimeter along the line of scan.

Referring to FIG. 6, the discharge tube 11B to be used in either of the second and the third embodiments comprises the cathodes 12-0, 12-11, 12-21, 12-31, the voltage inducing electrodes 14-0, 14-1, 14-2, and the styli 24-0, 24-1, 24-2, formed on an insulator plate 61 of ceramics, glass, or the like by the technique, such as evaporation, photoetching, plating, or the like, for manufacturing the integrated circuits. The styli 24-0, 24-1, 24-2, are extensions of the respective voltage inducing electrodes 14-0, 14-1, 14-2, with the pitch changed from 0.4 millimeter or more needed by the associated cathodes 12-0, 12-11, 12-21, to 0.25 millimeter or less required for attaining the desirable resolution. A start, a first, a second, and a third lead wire 62, 63, 64, and 65 for the start cathode 12-0, the first set of cathodes 12-11, 12-12, the second set of cathodes 12-21, 12-22, and the third set of cathodes 12-31, 12-32, are similarly formed on the insulator plate 61 together with the terminals 20, 41, 42, and 43. The start lead wire 62 and one of the first through the third lead wires 63, 64 and 65 are directly connected to the start cathode 12-0 and the corresponding set of cathodes. The remaining ones of the first through the third lead wires 63, 64 and 65 and the cathodes of the corresponding sets are connected together by metal wires 66-1, 66-2, 66-3, bonded thereto by way of, for example, supersonic bonding, avoiding the short circuits between the respective sets of cathodes. One edge 67 of the insulator plate 61 is bevelled to provide better contact between the outer ends of the styli 24-0, 24-1, 24-2, and the recording medium 25 shown in FIGS. 3 through 5. The discharge tube 118 further comprises the anode 13 formed on a similar insulator plate 71 by way of the integrated circuit manufacturing technique together with a terminal 72 therefor. The insulator plates 61 and 71 are hermitically sealed together along sealing margins 75 and 76 by a sealing material, such as frit, with a little space left therebetween and with the anode 13 brought into the position opposing the cathodes 12-0, 12-11, 12-21, 12-31, The assembly is evacuated through an exhaust pipe (not shown) attached preliminarily to the insulator plate 61 or 71. Subsequently, a gas or a mixture of gases, such as neon, is sealed in. it is known that addition of hydrogen to the gas sealed in makes it possible to raise the speed of scan.

Referring now to FlG. 7, a fourth embodiment of the instant invention comprises a gas discharge tube 11C which is similar to the discharge tube 115 as regards the elements designated by the like reference numerals. The discharge tube 11C comprises a plurality of aligned first anodes 13-0, 13-1, 13-2, 13-3, for the respective cathodes 12-0, 12-11, 12-21, 12-31, a like number of aligned intermediate electrodes 81-0, 81-1, 81-2, 81-3, disposed between the anodes 13-0, 13-1, 13-2, 13-3, and the cathodes 12-0, 12-11, 12-21, 12-31, to serve as the anodes for the respective cathodes and as the cathodes for the respective first anodes, and a similar number of aligned second anodes 82-0, 82-1, 82-2, 82-3, opposing the respective cathodes 12-0, 12-11, 12-21, 12-31, The voltage inducing electrodes 14-0, 14-1, 14-2, 14-3, are disposed adjacent the cathodes ends of the respective intermediate electrodes 81-0, 81-1, 81-2, 81-3, The first anodes 13 are connected in common to a dc. power source 17 through a first switching element (such as a transistor) 83 and a ballast resistor 16. The second anodes 82 are similarly connected to the d.c. power source 17 through a second switching element 84 and the resistor 16. A line start pulse generator 85 is connected between the start pulse terminal 20 and ground. A threephase guide pulse generator 86 is connected between the guide pulse terminals 41, 42, and 43 and ground. Each of the first anodes 13-0, 13-1, 13-2,'13-3, and the associated one of the intermediate electrodes 81-0, 81-1, 81-2, 81-3, form a first discharge path together with the related one of the cathodes 12-0, 12-11, 12-21, 12-31, Each of the second anodes 82-0, 82-1, 82-2, 82-3, forms a second discharge path together,

with the relevant one of the cathodes 12-0, 12-11,

12-21, 12-31, The fourth embodiment further comprises a pair of terminals 87 for supplying the picture signal assuming the values of logical 1" and "0 to the control terminal of the first switching element 83 and, through an inverter 88, to the control terminal of the second switching element 84.

if the picture signal-is subjected to negative modulation, the logical values 1 and 0 correspond to the black and the white levels, respectively. When the value of the, picture signal is logical l, the first switching element 83 becomes conductive to tire one of the first discharge paths depending on the pulse voltages 30, 46, 47 and 48, thereby supplying the concerned one of the styli 24-0, 24-1, 24-2, 24-3, with an electric potential approximately equal to twice the cathode drop minus the absolute value of the pulse voltage. When the value of the picture signal is logical 0, the second switching element 84 turns conductive to disable the first discharge paths and instead fire one of the second discharge paths, thereby removing the potential from the styli 24-0, 24-1, 24-2, 24-3,

Referring finally to FIG. 8, the discharge tube 11C to be used in the fourth embodiment is similar to those illustrated with reference to FIGS. 6 and 7 as regards the elements bearing the like reference numerals. The intermediate electrodes 81-0, 81-1, 81-2, and the second anodes 82 are formed on the first and the second insulator plates 61 and 71, respectively by way of the integrated circuit manufacturing technique. The tube 11C comprises an insulator member 91 serving as an ion barrier for preventing the ions produced at the first anodes 13 from adversely affecting the second discharge paths and for preventing the ions produced at the second anodes 82 from adversely affecting the first discharge paths, particularly, the voltage inducing electrodes 14-0, 14-1, 14-2, 14-3, as well as a spacer for precisely keeping the distances between the cathode ends of the intermediate electrodes 81-0, 81-1, 81-2,

and the first anodes 13 and between the cathodes 12-0, 12-11, 12-21, 12-31, 12-12, and the second anodes 82. The example depicted comprises a peripheral cylindrical spacer 92, which may preliminarily be made integral with the second insulator plate 71. The cathodes 12-0, 12-11, 12-21, 12-31, 12-12, and the cathode ends of the intermediate electrodes 81-0, 81-1, 81-2, may be of platinum. The anodes 13 and 82 may be of copper. The metal wires 66-1, 66-2, 66-3, may be of aluminum. The gas sealed in may be carbon dioxide at a pressure between 50 and 200 mmHg.

Instead of three sets of cathodes 12-11, 12-12, 12-21, 12-22, and 12-31, 12-32, it is possible to use n sets of cathodes in combination with an n-phase guide pulse generator, where n is an integer greater than three.

What is claimed is:

1. A device for recording an electric signal on an electrostatic recording medium including means for causing a gas discharge to scan a gas-filled space, first and second electrode means supplied with a first and a second electric potential, respectively, the potential difference between said potentials being dependent on said signal, and means for applying said potential difference to said recording medium wherein the improvement comprises first means operatively coupled to said first electrode means and responsive to said signal for varying the electric potential of said first potential, second means for deriving the electric potential of said space as said discharge scans said space, and third means for applying the derived potential to said second electrode means as said second electric potential.

2. A device as claimed in claim 1, wherein said second means comprises a plurality of voltage inducing electrodes placed in said space, whereby the electric potential of said space at the position of each said voltage inducing electrode is induced therein due to the electric conductivity given to said space by said discharge as said discharge reaches the position of the successive ones of said voltage inducing electrodes.

3. A device as claimed in claim 2, said second electrode means comprising a plurality of styli with which said medium is to be brought into contact, wherein said third means comprises means for connecting said voltage inducing electrodes to said styli, respectively.

4. A device for recording an electric signal on an electrostatic recording medium including means for causing a gas discharge to scan a gas-filled space, first and second electrode means supplied with a first and a second electric potential, respectively, the potential difference between said potentials being dependent on said signal, and means for applying said potential difference to said recording medium wherein the improvement comprises first means operatively coupled to said first electrode means and responsive to said signal for varying the electric potential of said space relative to said first potential, second means for deriving the electric potential of said space as said discharge scans said space, and third means for applying the derived potential to said second electrode means as said second electric potential wherein said space scanning means includes a plurality of aligned scan electrodes and atleast one opposing electrode placed in confronting relationship in said space, said scan electrodes being scanned by said discharge, wherein said voltage inducing electrodes are placed in said space confronting at least a predetermined number of said scan electrodes, respectively.

5. A device as claimed in claim 4, wherein said first 65 means comprises means for varying the electric potential of said scan electrodes relative to said first potential.

6. A device as claimed in claim 4, wherein said first means comprises means for varying the discharge current.

7. A device as claimed in claim 4, said scan electrodes and said opposing electrode serving as cathodes and first anode, respectively, wherein said first means comprises a plurality of intermediate electrodes disposed between said anode and said cathodes, respectively, to serve as the anodes for the respective ones of said cathodes and as the cathodes for said first anode, at least one second anode disposed in said space confronting the first-mentioned cathodes, and means responsive to said signal for interswitching said discharge between a first discharge path including said first anode and a second discharge path including said second anode, said voltage inducing electrodes being disposed between said first anode and said intermediate electrodes, respectively.

8. A device as claimed in claim 4, wherein said space is enclosed with two electric insulator plates sealed together, said scan electrodes and said voltage inducing electrodes being formed on the inside surface of one of said plates, said opposing electrode being formed on the inside surface of the other of said plates.

9. An electrostatic recording device comprising first and second electrode means disposed in a gasfilled space,

means, coupled to said first and second electrode means, for causing a gas discharge to scan the gasfilled space,

a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions,

a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and

means respectively interconnecting said group of electrodes to said styli electrodes.

10. A device as claimed in claim 9 further including means for selectively varying the electrical potential of the discharge experiencing space in accordance with an information signal whereby the potential induced in the electrodes of said group of electrodes varies in accordance with said information signal.

11. A device as claimed in claim 10 further including a back electrode placed in operable relationship with said styli electrodes and a recording medium placed in operable relationship with both said styli electrodes and said back electrode.

12. An electrostatic recording device comprising:

first and second electrode means disposed in a gasfilled space,

means, coupled to said first and second electrode means for causing a gas discharge to scan the gasfilled space,

a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said groupbeing induced in the respective electrodes in response to discharges at the electrode positions,

a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and

means respectively interconnecting said group of electrodes to said styli electrodes,

wherein said first electrode means comprises a plurality of discharge path electrodes, said group of electrodes being placed in said space in confronting relation to said discharge path electrodes and a plurality of discharge guide electrodes space alternately with respect to said discharge path electrodes, said device further including means for applying discharge scan inducing pulses to said discharge guide electrodes and means for applying an information signal to said discharge path electrodes.

13. An electrostatic recording device comprising:

first and second electrode means disposed in a gasfilled space,

means, coupled to said first and second electrode means, for causing a gas discharge to scan the gasfilled space,

a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions,

a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes,

means respectively interconnecting said group of electrodes to said styli electrodes, and

a back electrode placed in operable relation with said styli electrodes and the recording medium placed in operable relation with both said styli electrodes and said back electrodes and means for applying an information signal to said back electrode.

14. An electrostatic recording device comprising:

first and second electrode means disposed in a gasfilled space,

means, coupled to said first and second electrode means, for causing a gas discharge to scan the gasfilled space, I

a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions,

a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and

means respectively interconnecting said group of electrodes to said styli electrodes wherein said first electrode means comprises a plurality of electrodes, the device further including means for successively applying a discharge including pulse to each of said plurality of electrodes to cause a discharge to scan the space in synchronism with the application of said pulses to said plurality of electrodes.

15. A device as claimed in claim 14, further including means for applying an information signal to said second electrode means.

16. A device as claimed in claim 14 further including a back electrode placed in operable relation with said styli electrodes and a recording medium placed in operable relation with both said styli electrodes and said back electrode and means for applying an information signal to said back electrode.

17. A device as claimed in claim 15 wherein said means for applying an information signal to said second electrode means comprises, a discharge current control circuit receiving said information signal, said circuit controlling the discharge current in said space to thereby vary the potential induced in said group of electrodes.

18. An electrostatic recording device comprising:

first and second electrode means disposed in a gasfilled space,

means, coupled to said first and second electrode means for causing a gas discharge to scan the gasfilled space,

a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions,

a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and

means respectively interconnecting said group of electrodes to said styli electrodes wherein said first electrode means comprises a plurality of electrodes in one to one relationship with said group of electrodes, said device further including a plurality of intermediate electrodes disposed between said first electrode means and said second electrode means, said first electrode means serving as cathodes, said second electrode means serving as a first anode, said plurality of intermediate electrodes serving as anodes for respective ones of said plurality of electrodes comprising said first electrode means, second anode means disposed in said space confronting said first electrode means, means for applying for interswitching said discharge scan between a first discharge path including said first anode and a second discharge path including said second anode, said group of electrodes being disposed between said first anode and said intermediate electrodes.

19. A device as claimed in claim 18 further including means for successively applying discharge inducing pulses to said cathodes.

20. An electrostatic recording device for recording an information electrical signal on an electrostatic recording medium comprising means for causing a gas discharge to scan a gas-filled space exhibiting an electrical potential difference there-across,

means for selectively varying the electrical potential in said space in accordance with said information electrical signal,

inducing electrode means disposed within said space,

having induced thereon a potential proportional to the potential in said space in the vicinity of the discharge a plurality of styli coupled to said inducing electrode means, and

a recording medium in operable relationship to said plurality of styli,

whereby an electrostatic image corresponding to said information electrical signal is applied to said recording medium. I

21. The device as claimed in claim 20 further including a back electrode, said recording medium being disposed in operable relationship with said styli and said back electrode.

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1. A device for recording an electric signal on an electrostatic recording medium including means for causing a gas discharge to scan a gas-filled space, first and second electrode means supplied with a first and a second electric potential, respectively, the potential difference between said potentials being dependent on said signal, and means for applying said potential difference to said recording medium wherein the improvement comprises first means operatively coupled to said first electrode means and responsive to said signal for varying the electric potential of said first potential, second means for deriving the electric potential of said space as said discharge scans said space, and third means for applying the derived potential to said second electrode means as said second electric potential.
 2. A device as claimed in claim 1, wherein said second means comprises a plurality of voltage inducing electrodes placed in said space, whereby the electric potential of said space at the position of each said voltage inducing electrode is induced therein due to the electric conductivity given to said space by said discharge as said discharge reaches the position of the successive ones of said voltage inducing electrodes.
 3. A device as claimed in claim 2, said second electrode means comprising a plurality of styli with which said medium is to be brought into contact, wherein said third means comprises means for connecting said voltage inducing electrodes to said styli, respectively.
 4. A device for recording an electric signal on an electrostatic recording medium including means for causing a gas discharge to scan a gas-filled space, first and second electrode means supplied with a first and a second electric potential, respectively, the potential difference between said potentialS being dependent on said signal, and means for applying said potential difference to said recording medium wherein the improvement comprises first means operatively coupled to said first electrode means and responsive to said signal for varying the electric potential of said space relative to said first potential, second means for deriving the electric potential of said space as said discharge scans said space, and third means for applying the derived potential to said second electrode means as said second electric potential wherein said space scanning means includes a plurality of aligned scan electrodes and at least one opposing electrode placed in confronting relationship in said space, said scan electrodes being scanned by said discharge, wherein said voltage inducing electrodes are placed in said space confronting at least a predetermined number of said scan electrodes, respectively.
 5. A device as claimed in claim 4, wherein said first means comprises means for varying the electric potential of said scan electrodes relative to said first potential.
 6. A device as claimed in claim 4, wherein said first means comprises means for varying the discharge current.
 7. A device as claimed in claim 4, said scan electrodes and said opposing electrode serving as cathodes and first anode, respectively, wherein said first means comprises a plurality of intermediate electrodes disposed between said anode and said cathodes, respectively, to serve as the anodes for the respective ones of said cathodes and as the cathodes for said first anode, at least one second anode disposed in said space confronting the first-mentioned cathodes, and means responsive to said signal for interswitching said discharge between a first discharge path including said first anode and a second discharge path including said second anode, said voltage inducing electrodes being disposed between said first anode and said intermediate electrodes, respectively.
 8. A device as claimed in claim 4, wherein said space is enclosed with two electric insulator plates sealed together, said scan electrodes and said voltage inducing electrodes being formed on the inside surface of one of said plates, said opposing electrode being formed on the inside surface of the other of said plates.
 9. An electrostatic recording device comprising first and second electrode means disposed in a gas-filled space, means, coupled to said first and second electrode means, for causing a gas discharge to scan the gas-filled space, a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions, a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and means respectively interconnecting said group of electrodes to said styli electrodes.
 10. A device as claimed in claim 9 further including means for selectively varying the electrical potential of the discharge experiencing space in accordance with an information signal whereby the potential induced in the electrodes of said group of electrodes varies in accordance with said information signal.
 11. A device as claimed in claim 10 further including a back electrode placed in operable relationship with said styli electrodes and a recording medium placed in operable relationship with both said styli electrodes and said back electrode.
 12. An electrostatic recording device comprising: first and second electrode means disposed in a gas-filled space, means, coupled to said first and second electrode means for causing a gas discharge to scan the gas-filled space, a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being inducEd in the respective electrodes in response to discharges at the electrode positions, a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and means respectively interconnecting said group of electrodes to said styli electrodes, wherein said first electrode means comprises a plurality of discharge path electrodes, said group of electrodes being placed in said space in confronting relation to said discharge path electrodes and a plurality of discharge guide electrodes space alternately with respect to said discharge path electrodes, said device further including means for applying discharge scan inducing pulses to said discharge guide electrodes and means for applying an information signal to said discharge path electrodes.
 13. An electrostatic recording device comprising: first and second electrode means disposed in a gas-filled space, means, coupled to said first and second electrode means, for causing a gas discharge to scan the gas-filled space, a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions, a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, means respectively interconnecting said group of electrodes to said styli electrodes, and a back electrode placed in operable relation with said styli electrodes and the recording medium placed in operable relation with both said styli electrodes and said back electrodes and means for applying an information signal to said back electrode.
 14. An electrostatic recording device comprising: first and second electrode means disposed in a gas-filled space, means, coupled to said first and second electrode means, for causing a gas discharge to scan the gas-filled space, a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the position of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions, a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and means respectively interconnecting said group of electrodes to said styli electrodes wherein said first electrode means comprises a plurality of electrodes, the device further including means for successively applying a discharge including pulse to each of said plurality of electrodes to cause a discharge to scan the space in synchronism with the application of said pulses to said plurality of electrodes.
 15. A device as claimed in claim 14, further including means for applying an information signal to said second electrode means.
 16. A device as claimed in claim 14 further including a back electrode placed in operable relation with said styli electrodes and a recording medium placed in operable relation with both said styli electrodes and said back electrode and means for applying an information signal to said back electrode.
 17. A device as claimed in claim 15 wherein said means for applying an information signal to said second electrode means comprises, a discharge current control circuit receiving said information signal, said circuit controlling the discharge current in said space to thereby vary the potential induced in said group of electrodes.
 18. An electrostatic recording device comprising: first and second electrode means disposed in a gas-filled space, means, coupled to said first and second electrode means for causing a gas discharge to scan the gas-filled space, a group of electrodes disposed in said gas-filled space between said first and second electrode means, the electrical potential of said space at the positIon of each of the electrodes in said group being induced in the respective electrodes in response to discharges at the electrode positions, a group of styli electrodes corresponding in number to the number of electrodes in said group of electrodes, and means respectively interconnecting said group of electrodes to said styli electrodes wherein said first electrode means comprises a plurality of electrodes in one to one relationship with said group of electrodes, said device further including a plurality of intermediate electrodes disposed between said first electrode means and said second electrode means, said first electrode means serving as cathodes, said second electrode means serving as a first anode, said plurality of intermediate electrodes serving as anodes for respective ones of said plurality of electrodes comprising said first electrode means, second anode means disposed in said space confronting said first electrode means, means for applying for interswitching said discharge scan between a first discharge path including said first anode and a second discharge path including said second anode, said group of electrodes being disposed between said first anode and said intermediate electrodes.
 19. A device as claimed in claim 18 further including means for successively applying discharge inducing pulses to said cathodes.
 20. An electrostatic recording device for recording an information electrical signal on an electrostatic recording medium comprising means for causing a gas discharge to scan a gas-filled space exhibiting an electrical potential difference there-across, means for selectively varying the electrical potential in said space in accordance with said information electrical signal, inducing electrode means disposed within said space, having induced thereon a potential proportional to the potential in said space in the vicinity of the discharge a plurality of styli coupled to said inducing electrode means, and a recording medium in operable relationship to said plurality of styli, whereby an electrostatic image corresponding to said information electrical signal is applied to said recording medium.
 21. The device as claimed in claim 20 further including a back electrode, said recording medium being disposed in operable relationship with said styli and said back electrode. 